It was noteworthy that Gordon disagreed with Obama’s decision, and agreed with the criticism of U.S. allies, because he is known, in national-security circles, for being extremely wary of the consequences of deeper U.S. involvement in Syria (in this, he resembles his successor, Robert Malley, who is now Obama’s coordinator for anti-ISIS activities). I asked Gordon if he would speak to me on the record about these events, and he agreed. A full transcript of our conversation appears below, but here are some highlights:

On the red-line issue, Gordon said, “Without denying the president’s concerns about a slippery slope,” that it “would have been possible to say that this is not about changing the regime in Syria, it’s not about going to war in Syria—but when the United States says you can’t use chemical weapons, you can’t use chemical weapons.” He went on to say, “I accept that there was some risk of a slippery slope if he used CW again. But Assad would also have had to run that risk, and that’s just the dynamic that you’re in, so we needed to plant in his mind that if he tested our resolve, well, he was running a pretty big risk, too. And that might not be in either of our interests, but it certainly wouldn’t be in his. … This was a more limited and therefore more achievable objective than regime change. What he would be saying is, ‘I’m going to try to stop them from gassing people because if I don’t, we are essentially saying, you can use chemical weapons as much as you like.’”

Obama’s decision to stand down from an attack on Assad’s forces has, in some minds, been vindicated—in an ad hoc, post-facto way—because the Russian president, Vladimir Putin, soon worked with him to remove most of Assad’s chemical-weapons stockpiles. I asked Gordon if he thinks the president still could have gotten the stockpiles out of Syria, had he carried out his threat to strike. “I think he would have been even more likely to get it,” Gordon said. “As it turns out, we got lucky. My concern at the time was … that the next time we say to someone, ‘There are consequences if you act,’ we won’t really mean that. I think that this has repercussions in Europe, in Asia, and elsewhere. I think sometimes, on the credibility point, on the deterrence point, you actually have to be willing to do things that are a cost to you.”